Electrical connectors are known which contain one or more contacts, which are mountable in cutouts of bulkheads to be matable with corresponding contacts of electrical connectors on opposite sides of the bulkheads. Such an interface connector must maintain a hermetic seal at the bulkhead cutout which survives substantial and rapidly changing differences in atmospheric pressure on both sides of the bulkhead, and maintain that hermetic seal at elevated and reduced temperatures over long in-service use and through many cycles of pressure and temperature changes, and also through rapid temperature changes such as is known as thermal shock.
One known type of interface connector utilizes a plate of an electrically conductive metal such as KOVAR iron/nickel/cobalt alloy (trademark of Carpenter Technology Corporation) in which the plate is disposed transversely within and directly soldered to a tubular outer housing, and the outer housing can include an annular flange portion soldered to the periphery of the bulkhead cutout. In hermetically sealed interface connectors incorporating a metal plate, the individual contact pins are commonly retained within passageways in the metal plate by glass or ceramic plugs which support the contacts and provided a hermetic seal between the contacts and the side walls of the passageways. The glass plugs commonly are of borosilicate glass which has a coefficient of thermal expansion which is matched or at least quite similar to that of the KOVAR alloy. In the manufacture of this type of connector several process steps are performed involving very high temperatures: to decarburize or drive off carbon from the metal; to form a thick enough oxide layer on the metal; and to melt the glass preforms in the plate passageways and about the contacts to form a hermetic seal with the oxide layer.
A standard type of connector mating interface is known wherein one of two mating rectangular-shaped connectors has a dielectric housing surrounded by and affixed within a metal shell having a D-shaped hood surrounding the plurality of contacts providing physical protection and EMI shielding to the contact sections extending outwardly from the connector housing, the D-shaped hood adapted to receive thereinto a corresponding D-shaped plug section of the housing of the mating connector, while the metal shell is electrically commoned with the metal shell of the mating connector. The D-shape provides polarization so that the connector can be mated in only one orientation, resulting in the individual contacts of one of the connectors being aligned with and mating with the appropriate contacts of the other connector. The metal shells also include transverse flanges extending outwardly at the ends of the mating interface of the connectors and containing apertures, enabling the connectors to be fastened together after mating such as by jackscrews or similar accessories.
One such D-shaped connector assembly is known which is specified by a standard known as MIL-C-24308C, in which a metal plate is utilized instead of a dielectric housing, and includes passageways containing the contacts utilizing glass plugs. The metal plate is of steel and is joined by brazing to the surrounding metal shell of brass, which are plated by tin over copper. The passageways are formed in the metal plate by drilling, and each passageway is identified by permanent visible indicia stamped into the metal plate to indicate the contact position. The contacts are ferrous alloy plated with gold over copper, and the glass is a compression glass. The connector must meet stringent performance requirements set forth in MIL-STD-1344A, regarding no mechanical damage, nor open circuits, nor leakage of air under pressure differential, after the connector in mated engagement with its mating connector is subjected to random vibration, mechanical shock, sinusoidal vibration, and temperature cycling; and the connector must meet a satisfactory dielectric withstanding voltage.
Where such connectors have two or more metal parts to be brazed or otherwise integrally joined together peripherally around the contact region of the metal plate, it is necessary that the abutting surfaces to be brazed be absolutely coplanar and abut at all locations surrounding the contact region, or weaknesses can result possibly leading to undesired leakage under pressure and especially at elevated temperature. Another necessity is that the metal-to-metal interface not permit leakage where the two metals have different coefficients of thermal expansion which may stress the brazed joint; this problem interrelates with the previously stated problem of non-coplanar abutting surfaces, in that where substantial brazing material is disposed between the incremental gaps at a location, the coefficient of thermal expansion of the brazing material itself can result in leakage when different from the coefficients of the adjacent metals. Further, there is the known problem of galvanic corrosion between different metals during in-service use which eventually could affect hermeticity.
One other concern is that during stamping of the visible indicia onto the surface of the contact region of the metal plate adjacent the respective contact passageways, the passageway walls may be incrementally deformed so that the passageway walls originally precisely drilled contain regions of less than nominal diameter at least adjacent the surface stamped, which can result in possible leakage sites after the hermetic glass plugs are formed surrounding and retaining the respective contacts extending through the passageways. Such deformities could also complicate assembly of the glass preforms into the passageways during contact loading. The stamping may also result in slight warping of the metal plate which may disturb the originally precisely axial alignment of the passageways and corresponding alignment of the contacts extending therethrough.
It is desired to provide a hermetically sealed connector which maintains a precisely planar metal engagement surface to abut and either be soldered to the bulkhead cutout, or be adapted to firmly sealingly engage the bulkhead entirely surrounding the cutout.
It is also desired to provide a hermetically sealed connector which maintains precise positioning and precise axial alignment of the contacts extending through the transverse metal plate.
It is further desired to provide that the contacts have concentric outer surfaces and the passageways have walls which are precisely concentric of a continuous nominal diameter therealong, and that the contacts be maintained precisely coaxial with respect to respective passageways so that all portions of the passageway walls are maintained a fixed minimum distance radially from the contact portions.
It is also further desired that the axes of the several passageways of the array are precisely perpendicular to the support plate so that the pins of the array are coparallel.